so my daughter recently purchased a 07 Liberty to learn how to drive in. and driving down the road the other day, the check engine light came on. after pulling the code, its showing that the (i think) upstream O2 sensor has a hi temp reading? I am pretty good at replacing parts, and fixing mechanical issues. but i am NOT good with computer and electrical gremlins. I really don't know how important this is. is it something that NEEDS replacing? and what will happen if she just continues to drive it this way?